In the jewelry trade, rope chains are typically manufactured by hand or machine, by interlinking individual links, into the shape of a double helix. This procedure provides a rope appearance. The peripheral surface of the resulting rope chain comprises an undulating shape. Several different weaving techniques may be used and the resulting individual links can have different shapes. There might be a different number of links in the chains; eg., three, four, five, etc. links might be inserted into one link. These chains might be solid, when each link is formed by a solid wire, or when it is stamped on a plate; or they might be hollow, when the links are formed by hollow tubes or tube sections. In the fine jewelry industry, these links are made with precious metals or alloys of precious metals.
The finish of the products is very important in precious metal jewelry. Based on the principle that a jewel must stand out and, therefore, "shine" i.e. reflect light brilliantly, jewelry manufacturers are constantly searching for new ways to improve the reflectance of their products.
If the chain is formed of links made with a solid wire and a circular cross-section, the cross-section of the rope chain will take the form shown in FIG. 1. If the links used to form the rope chain have square or rectangular cross-sections, whether in the form of square tubes or rectangular stamped plates, the cross-section of the rope chain may take the form shown in FIG. 2. Neither of the rope chains shown in FIGS. 1 or 2 have a smooth, continuously curved peripheral surface. The chain shown in FIG. 1 has a periphery made up of a series of small curved segments while the cross-section of FIG. 2 comprises an irregular surface with uneven, exposed edges. Those skilled in the art will appreciate that a chain such as that shown in FIG. 2 may have a tendency to become snagged on garments.
For several years, most rope chains had one of types of finish. A first type of finish was used for the solid chains as well as for the hollow chains. This type of finish preserved the original form of the links. These could be circular, oval, square, rectangular, etc. The shine of this chain type was achieved through various processes, such as: chemical cleaning, commonly known as bombing, or electrolytic processes, known as stripping; which could be combined with a tambouring, polishing or electrolytic silver plating processes. The shine quality of the resulting chain is a function of the alloy employed and of the uniformity of the wire or tube surface from which the link is made.
Rozenwasser's U.S. Pat. No. 5,303,540 teaches a method of obtaining a more intense shine on hollow rope chain. This method uses a link manufactured from a thin plate that has been planed or polished in a band that will form the external surface of the upper circumference of the link. The finished chain has the original shape of the links from which it is made, but more shine because the peripheral surface of the links purportedly obtains a better finish than earlier processes normally employed for the manufacturing of a hollow rope chain.
A second finishing method is the diamond cut process. The name of the "diamond cut" process and, therefore, the name of the chains so processed originates from the word diamond, because, the goal is that the resulting chain shines like a diamond. A diamond shines due to its cut and polished facets which reflect light with great intensity. The diamond cut process simulates the facets of a diamond by making facets in a regular finish chain. This type of finish is based on the principle that light will be reflected more by polished flat surfaces than other kind of surfaces. For that reason, surfaces are cut on the chain by using processes commonly employed in the jewelry industry, such as "ice-lathe to diamond" cutting processes performed with diamond milling machines, or, with extremely polished cutting tools. The result of said processes are extremely polished flat surfaces on the chain.
The diamond finish can be achieved with a different number of facets or cuts. However, the most common diamond cut has 4 or 8 facets as shown in FIGS. 3, 4 and 5.
The diamond cut process is used most commonly to diamond cut a solid like rope chain. In the case of a hollow link rope chain, a link can be deformed with a non-sharp tool to create flat surfaces simulating the facets of a diamond. Afterwards, a sharp tool may be employed to obtain a polished surface in each facet, so that the chain has a similar finish to a diamond cut solid chain. U.S. Pat. Nos. 5,125,225 and 5,129,220 by Strobel teach methods of placing facets in hollow link chains.
Other methods have been suggested for enhancing the finish of a jewelry chain or methods of obtaining improved finishes on such chains. For example, U.S. Pat. No. 4,716,750 of Tizzi discloses rotary swaging and annealing, repeated in sequence, to produce hollow articles with various tubular cross-sections. U.S. Pat. No. 4,754,535 of Valtiero discloses the use of ice as a packing material support for surface alteration of thin continuous stock. U.S. Pat. Nos. 2,424,924 of Chernow and 2,711,069 to Ambrust describe methods of producing ornamental facets on solid wire chain links through grinding operations. U.S. Pat. Nos. 3,083,002 of Lacey and 4,268,946 of Einseberg disclose the use of a solidifying material, such as ice, as a chuck to hold jewelry workpieces in place. Both of these patents are directed to cutting thin metal workpieces. The Eisenberg '946 patent particularly directed toward cutting tubular members.
U.S. Pat. Nos. 2,895,290 of Devonshire, 3,410,085 to Sheth, 4,679,391 to Tizzi and 4,682,467 to Waltmeyer disclose stamping impressions into solid chain links. The '391 patent is particularly directed toward jewelry.
U.S. Pat. No. 4,681,664 of Eberle discloses the altering or reinforcing of hollow thin walled jewelry articles by electroforming at stress points (such as at joints to increase their strength). U.S. Pat. No. 4,996,835 of Rozenwasser discloses the use of both solid and hollow links in jewelry rope chains, and German Patent No. 2,428,647 appears to disclose the use of a solidifying agent as a chuck to hold workpieces.
U.S. Pat. Nos. 5,125,225 and 5,129,220 by Strobel reveals the deformation of hollow annular links of a chain, in order to get flat surfaces on the chain that simulate the appearance of diamond cut solid chains.
U.S. Pat. No. 5,303,540 by Rozenwasser describes a process of manufacturing hollow links with the link's upper part polished. This results in a hollow chain finish where each link has a high shine on the surface of the external circumference.
While the previous disclosed methods of finishing jewelry rope chains have increased the reflectance of the peripheral surfaces of those chains, such peripheral surfaces are most often formed of a series of flat reflective surfaces, which only reflect light to the eyes of an observer if the particular reflective surface was positioned at a proper angle relative to the source of light. If the angle defined by the source of light, the reflective surface, and the eye of the observer was not correct then the observer would not observe light reflected brilliantly off one of the flat surfaces. For example, with a rope chain having flat facets such as those described above, if a particular facet is properly oriented for reflecting light directly from a source of light to a stationary observer, the observer would observe a brilliant reflection. However, if the rope chain was rotated slowly the observer would not observe a brilliant reflection until the adjacent facet was properly oriented between the source of light and the observer's eye. Therefore, it will be appreciated that the use of flat faceted reflective surfaces does not provide a "continuous" reflectance.
It would therefore be desirable to increase the duration of the pleasant high reflectance observed by a person viewing a jewelry rope chain.
It would also be desirable to provide a method for forming jewelry rope chains having continuous reflectance, whether formed of solid or hollow links.